With the development of technology, the power system for the electric vehicles (EV) is designed to be smaller, for being fitted in various types of electric vehicles. In addition, the power system has been developed to be more powerful; for example, the power electronic unit (PEU) in the power system is equipped with more power devices (e.g. transistor) or higher performance power devices. Hence, a heat dissipation system is adopted to dissipate heat generated by the power devices. An ideal heat dissipation device should dissipate the heat generated by the power device timely no matter the power device is at the rated output or the peak output. In such a case, the ideal dissipation device is designed large in size in order to timely dissipate the heat generated by the power device at the peak output.